1. Field of the Invention
The present invention relates generally to a blower unit for use in an automotive air-conditioner, for example, and more particularly to an apparatus for preventing generation of noise caused by resonance of a blower unit using a brushless motor.
2. Description of the Prior Art
When a brushless motor vibrates at a frequency which is equal to the natural frequency of a blower unit, the resonance phenomenon takes place, leading to generation of an enhanced operation noise. To cope with this difficulty, the brushless motor disclosed in Japanese Utility Model Laid-open Publication No. 58-153582 is provided with a yoke made of a dumping material to limit or lower the vibration of the brushless motor even when the resonance takes place.
The damping yoke thus provided is, however, unable to dampen the vibration completely so that a vibrational noise can still be generated when a high harmonic of vibration of the brushless motor is coincident with the natural frequency of the blower unit.